/* gmp_urandomm_ui -- uniform random number 0 to N-1 for ulong N.
Copyright 2003, 2004 Free Software Foundation, Inc.
This file is part of the GNU MP Library.
The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of either:
* the GNU Lesser General Public License as published by the Free
Software Foundation; either version 3 of the License, or (at your
option) any later version.
or
* the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any
later version.
or both in parallel, as here.
The GNU MP Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
You should have received copies of the GNU General Public License and the
GNU Lesser General Public License along with the GNU MP Library. If not,
see https://www.gnu.org/licenses/. */
#include "gmp-impl.h"
#include "longlong.h"
/* If n is a power of 2 then the test ret 1
a[1] = 0;
#endif
count_leading_zeros (leading, (mp_limb_t) n);
bits = GMP_LIMB_BITS - leading - (POW2_P(n) != 0);
for (i = 0; i < MAX_URANDOMM_ITER; i++)
{
_gmp_rand (a, rstate, bits);
#if LIMBS_PER_ULONG == 1
ret = a[0];
#else
ret = a[0] | (a[1] << GMP_NUMB_BITS);
#endif
if (LIKELY (ret < n)) /* usually one iteration suffices */
goto done;
}
/* Too many iterations, there must be something degenerate about the
rstate algorithm. Return r%n. */
ret -= n;
ASSERT (ret < n);
done:
return ret;
}